1. Field of the Invention
This invention relates to a battery pack which is removable from a portable electronic appliance such as a portable telephone and notebook-size personal computer, and a method of manufacturing the battery pack.
2. Description of the Related Art
Conventionally, a battery pack incorporating a battery such as a lithium ion battery or manganese battery has been prepared for a portable telephone and notebook-size personal computer. The battery pack is adapted to be removable from a body of the portable telephone. The battery pack permits the portable telephone to be used for a certain time with no power supply from a commercial power source.
FIG. 11 is a perspective view showing an example of such a battery pack. FIG. 12 is a perspective view of a circuit board incorporated in the battery pack. The battery pack 1 includes a vessel 2 made of resin and a circuit board 3 connected to a battery (not shown). The circuit board 3 includes a protecting circuit (not shown) for excessive charging and excessive discharging.
As seen from FIG. 12, the circuit board 3 is provided with a terminal stand 4 mounted on its surface and a connecting terminal 7 for connection to the battery. The terminal stand 4 includes a plurality of contact terminals 5 on the upper surface. The circuit board 3 is supported inside the vessel 2 so that the contact terminals 5 are exposed externally through an opening 6 formed on the surface of the vessel 2. The circuit board 3 is adapted to be electrically connectable to a body of the portable telephone in such a manner that the contact terminals 5 on the terminal stand 4 are brought into contact with connector pins (not shown) formed on the body of the portable telephone. Namely, the circuit board 3 supplies power to the body and charges the battery through each of the contact terminals 5 on the terminal stand.
In recent years, for the portable telephone, reduction in component cost and production cost as well as reduction in weight and thickness has been demanded. This also applies to the battery pack which is removed from the portable telephone. However, the terminal stand 4 on the circuit board 3 in the battery pack 1 is generally expensive. This influences the component cost in the entire appliance. In addition, the terminal stand 4 is relatively high in the mounting height to the circuit board 3. This influences the size of the battery pack, thus violating the demand of reduction in the weight and thickness.
This invention has been accomplished in order to overcome the inconvenience described above.
An object of this invention is to provide a battery pack which can realize reduction in the weight and thickness and also reduce the production cost.
Another object of this invention is to provide a method for manufacturing such a battery pack.
In order to attain the above objects, in accordance with the first aspect of this invention, there is provided a battery pack comprising a vessel, a battery mounted in the vessel and a circuit board connected to the battery, wherein an opening is formed on the surface of the vessel and thin-film terminal portion is formed on the surface of the circuit board so that it is exposed externally through the opening. Concretely, the terminal portion includes a base layer formed on the circuit board and a plated layer formed on the base layer, and the plated layer is made of gold.
In accordance with this invention, the terminal portion of the circuit board, which is to be connected to a body of e.g. a portable telephone and incorporated in the battery pack, is formed as a thin film on the circuit board. For this reason, as compared with the conventional structure provided with an electronic component such as a terminal stand, the structure according to this invention can reduce the component cost and also decreases the mounting height of the components on the circuit board. Thus, the thickness of the battery pack can be reduced. This contributes to reduction in thickness, size and weight of the portable telephone. In addition, the plated layer constituting the uppermost layer of the terminal portion, which is made of gold, increases the anti-corrosiveness and decoration.
In a preferred embodiment of this invention, on the circuit board, an insulating layer is formed in the other area than the area where the terminal portion is formed, and the insulating layer is formed so as to cover a peripheral edge of the plated layer so that the surface of the circuit board and/or the surface of the base layer are not exposed externally. Conventionally, as the case may be, the following event occurred. Owing to the heat generated when the plated layer is formed, the material of the insulating layer contracts so that a gap is generated between the base layer and the insulating layer formed in the other area than the terminal portion is formed. Therefore, when the surface of the base layer and surface of the circuit board are exposed externally through the gap, water or the like invades the gap, and deteriorates the plated layer. However, if the insulating layer is formed so as to cover sufficiently the peripheral edge of the plated layer which is the uppermost layer, even if the insulating layer contracts slightly, generation of such a gap is prevented. Therefore, the surface of the base layer 14 is not exposed externally. This prevents invasion of water, thereby suppressing the surface deterioration of the plated layer. Accordingly, the battery pack which is reliable can be provided.
In accordance with the second aspect of this invention, there is provided a method of manufacturing a battery pack having a vessel, a battery mounted in the vessel and a circuit board connected to the battery, comprising:
a step of forming a terminal portion in manufacturing the circuit board, the step of forming a terminal portion being to stack a base layer of copper and a plated layer of copper successively to form the terminal portion.
In accordance with the manufacturing method described above, the circuit board of the battery pack according to the first aspect of this invention can be easily realized. For this reason, the same effect as that of the battery pack according to the first aspect can be obtained.
Preferably, the method of manufacturing a battery pack further comprises:
a step of forming an insulating layer after the step of forming a terminal potion in manufacturing the circuit board, the step of forming an insulating layer being to form an insulating layer in the other area than the area where the terminal portion is formed, wherein the insulating layer is formed so as to cover a peripheral edge of the plated layer so that the surface of the circuit board and/or the surface of the base layer are not exposed externally. In accordance with this invention, since the insulating layer is formed after the base layer and plated layer have been formed, the insulating layer can be easily formed so as to cover the peripheral edge of the plated layer. For this reason, the same effect as that of the battery pack according to the first aspect can be obtained.
Preferably, said plated layer is protruded on the surface of the insulating layer. In accordance with this invention, secure contact with outer circuit can be obtained.
Preferably, said insulating layer is made of epoxy resin. In accordance with the present invention, since the epoxy resin has elasticity, secure contact with outer circuit can be obtained.
Preferably, said circuit board is a hybrid integrated circuit comprising protecting circuit for excessive charging and excessive discharging.
The above and other objects and features of this invention will be more apparent from the following description taken in conjunction with the accompanying drawings.